Oligomerization of isobutene-containing feedstocks

ABSTRACT

The invention relates to the use of isobutene-containing olefin feedstock in oligomerization reactions, particularly in the production of octenes as feedstock for the manufacture of plasticizer alcohols, the process comprising contacting a feed comprising isobutene with a molecular sieve at a temperature in excess of 240° C. to produce a product low in triple-branched octenes.

FIELD OF THE INVENTION

The invention relates to the use of isobutene-containing olefinfeedstock in oligomerization reactions, and in preferred embodiments theuse of raffinate in the production of octenes as feedstock for themanufacture of plasticizer alcohols.

BACKGROUND OF THE INVENTION

The oligomerization of light olefins to heavier olefins is important forthe production of gasoline, distillate, and feedstock for otherprocesses. In these oligomerization processes typically C3 to C6 olefinsand mixtures thereof are contacted with zeolite or solid phosphoric acid(SPA) catalyst under oligomerization conditions and converted to dimers,trimers, and other oligomers (low molecular weight polymers). Theproducts may be useful “as is”, or they may be further processed, suchas by hydrogenation or to produce functionalized products.

By way of example, a typical direct product of dimerization of C4olefins is trimethyl pentene, useful as an octane enhancer. See, forinstance, U.S. 2004/0181106 and U.S. 2004/0030212. In this regard, thepresence of isobutene in the feed enhances the production of the desiredhighly branched product.

Isobutene in light olefin oligomerization to gasoline in Catpoly unitsis also useful for improved octane values. Recent work to displace solidphosphoric acid with zeolites has shown that typically zeolites areexcellent catalysts for producing highly branched, high octane oligomersfrom isobutene containing feeds. See “EMOGAS Technology for CatpolyUnits”, presented at the National Petrochemical & Refiners AssociationAnnual Meeting, Mar. 13-15, 2005, San Francisco, Calif.; and U.S.Application No. 2004/0181106 A1.

The octenes produced by the aforementioned dimerization may instead bereacted with carbon monoxide and hydrogen in the well-known Oxo Process,to produce C9 aldehydes and/or alcohols. See, for instance, U.S. PatentApplication No. 2005/0119508.

C9 aldehydes and/or alcohols have many uses and are particularly highlyvalued in the production of plasticizers, e.g., triisononyl phthalate.See, for instance, U.S. Pat. Nos. 3,657,150 and 6,969,736. The presenceof isobutene has, in the past, presented problems in the production ofplasticizers. As a result, the prior art concerning the use of zeolitesto produce higher olefins for plasticizer production has in some casesfocused on the presence of isobutene in the feedstock.

U.S. Patent Application Publication 2004/0006250 (WO 01-83407A1) teachesthat the feedstock may comprise butenes obtained from refining orcracking and may comprise mixtures of n-butenes and isobutene havingfrom a few wt % of isobutene up to 30 to 40 wt % isobutene at 140 to240° C. A particular example discloses a mixed n-butene and isobutenefeed to H-ZSM-57 with conditions adjusted to maintain total alkeneconversion above 95%. In one example a feed comprising about 8 wt %isobutene gave a product comprising about 6.5 wt % trimethypentene withabout 80 wt % octene selectivity.

C4 linear olefins are an attractive feedstock for producing octenes withzeolite catalysts because, among other reasons, the resulting octeneshave triple branching of less than about 5 wt %. When isobutene is addedto the oligomerization feedstock, the amount of triple-branched octenesincreases to a level which is unacceptable for some end uses such ascertain plasticizers.

The amount of isobutene in C4 streams typically obtained from therefinery operations (i.e., raffinate-1, or “raff-1”) is greater than theamount used in current commercial oligomerization reactions leading toOxo Process feedstock. Thus, isobutene is removed, yielding a product,“raff-2”, useful in the Oxo Process for plasticizer-grade C9 alcohols.The isobutene removed in this step could be used in the production of,for instance, MTBE. However, with the phase out of MTBE, the usualintegrated commercial process—where raff-1 was converted to raff-2 andsimultaneously supplying the feed to Oxo and MTBE processes—is no longerpractical.

Accordingly, for these reasons, it would be highly desirable if aprocess could be found to dimerize raff-1 directly, without a step ofremoval of all or a portion of isobutene, to yield a C8 product directlyuseful in the Oxo Process without removal of isobutene.

There is an extensive prior art teaching the use of zeolites for lightolefin oligomerization, particularly for uni-dimensional 10-ringzeolites such as ZSM-22, ZSM-23, and SAPO-11. See, for instance, U.S.Pat. Nos. 4,962,249; 5,026,933; EP 0703888; EP 0625132; and EP 0757976.The present inventors have surprisingly discovered a process whereinmultidimensional zeolites can, in embodiments, be used to oligomerizehigh isobutene-containing feedstocks, such as raffinate-1, to provide aproduct low in triple branched octenes.

SUMMARY OF THE INVENTION

The invention is directed to the oligomerization of isobutene-containingfeedstocks over molecular sieves, preferably zeolites, and morepreferably zeolites having the MFS structure type, to produce a productlow in triple-branched octene isomers. In embodiments the catalystscomprise multi-dimensional molecular sieves containing at least one 10or 12 ring channel system, e.g., ZSM-57.

The invention is also directed to a process for making functionalized C9products (e.g., alcohols) comprising oligomerization ofisobutene-containing raffinate-1 followed by reaction of at least aportion of the oligomerization product in the Oxo Process.

It is an object of the invention to provide an improved process for theoligomerization of isobutene, especially raffinate-1, wherein theimprovement comprises producing a product having a decreased amount ofbranched octenes that is advantageously used in the Oxo Process toprovide plasticizer-grade C9 alcohols.

It is still another object of the invention to provide, in embodiments,a process of oligomerizing high isobutene-content olefin feeds toprovide selectively an octene product having less than 10 wt %triple-branched octene product with a branching index (BI) of less than1.9, at temperatures in excess of 240 C. (reactor inlet temperature) andbutene conversion rates of between about 80 and 95%.

These and other objects, features, and advantages will become apparentas reference is made to the following detailed description, preferredembodiments, examples, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the octene selectivity versus buteneconversion using a ZSM-57 catalyst.

FIG. 2 is a graph showing octene triple branching versus buteneconversion using a ZSM-57 catalyst.

FIG. 3 is a graph showing octene branchiness (BI) versus buteneconversion using a ZSM-57 catalyst.

DETAILED DESCRIPTION

According to the invention, isobutene-containing feedstocks areoligomerized over molecular sieve catalysts effective for theoligomerization of C3 to C6 olefins to dimers and higher orderoligomers, particularly over zeolites and even more preferably overzeolites having the MFS structure, as defined by the IZA structurecommission and published in “Atlas of Zeolite Structure Types” by W. M.Meier et al., 4th revised Ed. Elsevier, London 1996. ZSM-57 is thepreferred zeolite.

The preferred catalyst is ZSM-57, at least partially if not wholly inacidic form.

By “isobutene” is meant 2-methyl propene (or isobutylene).

The feedstock may more broadly be selected from and/or comprise amixture of isobutene with one or more other C3-C6 linear and/or branchedolefins (alkenes). In preferred embodiments the feedstock may compriseraffinate-1 or raff-1, the terms used interchangeably herein.

The preferred feedstock is raffinate-1, which is used interchangeablyherein with “raff-1”.

By “raff-1” is meant a C4 feedstock comprising >40% olefins and <1 wt %dienes obtained from FCC or thermal cracking units (e.g. cokers,visbreakers, and steancrackers) or combinations thereof. Raff-1 istypically obtained from a feedstock containing a broader range ofhydrocarbons, typically C3 through C5. The mixed carbon number feed issent through a depropanizer to remove C3 hydrocarbons and then through adebutanizer to remove C5+ hydrocarbons. The mixed C4 feedstock obtainedin this fashion from steamcrackers contains 10 to 40 wt % butadiene. Toobtain a raff-1 stream, the mixed steamcracker C4's are mixed withhydrogen and passed over a catalyst which selectively converts butadieneto linear butenes to provide a mixture of isobutene, n-butenes,isobutane, and n-butane with <1 wt % butadiene.

In addition to isobutene, the feedstock may contain a single otheralkene or multiple other alkenes, mixtures of linear and branchedalkenes with the same carbon number or mixtures of linear and/orbranched alkenes with different carbon numbers. For example, suitablefeedstreams include mixed C₃ and C₄ olefinic feeds obtained fromrefining, cracking (catalytic cracking or steam cracking) and/orreforming of oils, butane-butene fractions obtained by removing orselectively hydrogenating butadiene from C₄ by-product fractions formedin the production of ethylene by thermal cracking of oils (suchfractions contain mixtures of n-butenes and isobutene having from a fewwt % of isobutene up to 30 to 40 wt % isobutene) or C₄ hydrocarbonmixtures obtained by dehydrogenation of hydrocarbon mixtures containingn-butane and isobutane.

A particular embodiment of the invention relates to processes using afeedstock in which isobutene represents about 8 to about 40 wt %, suchas from about 8 or 9 or 10 or 11 or 12 or 13 or 14 wt % to about 20 or25 or 30 or 34 or 36 or 38 or 40 wt % isobutene, with ranges from anylower limit to any higher limit being envisioned, such as from 12 to 34wt %, or from 8 to 20 wt %, or 12 to 20 wt %. Unless otherwisespecified, through the specification when wt % of an olefin is referredto, it is based on the weight of all the olefins in the feedstock,whether mono-olefins or otherwise (such as butadiene); i.e., theparaffin content is ignored. Thus, for example, a feedstock comprised of12 wt % isobutene, 48 wt % n-butenes, and 40 wt % butanes is computed tohave an isobutene content of 20 wt %.

The feedstock may also comprise an inert diluent. The diluent istypically comprised of C2-C6 paraffins.

In preferred embodiment, the feedstock consists essentially of a mixtureof isobutene (such as in any of the amounts specified above), one ormore other C3-C6 linear and/or branched olefins (such as in the amountof 1 wt % to about less than 50 wt %), remainder paraffin diluent. Inthe most preferred embodiment, the feedstock consists essentially of araff-1

In embodiments, using isobutene containing feedstocks, the process givesan oligomeric product low in triple-branched isomers, i.e., thatcontains from 2 to 15 wt % trimethylpentenes, preferably from 2 to 10 wt% trimethylpentenes, or 2 to 8 wt % trimethylpentenes, with respect tothe total weight of octenes in the oligomeric product.

The average branchiness of the octenes produced by the process of theinvention may be low, such as below 1.8 or 1.7, or even 1.6, buttypically will range from 1.6 to 2.2, such as from about 1.6 to 2.2, or1.7 to 2.0 or 1.7 to 1.9. Branchiness is defined as the number ofbranches per molecule or moiety (e.g., octene), and Branching Index (BI)is given here as the average number across the sample. Thustrimethylpentene has a branchiness of 3.0. A mixture of 50 mol %trimethylpentene and 50 mol % dimethylhexene has a BI of 2.5.

The catalyst may be chosen from among a variety of zeolites active foralkene oligomerization reactions (i.e., a catalyst other than solidphosphoric acid (SPA)). The preferred catalysts are multidimensional 10and 12 ring zeolites such as zeolites having the MFS (e.g., ZSM-57), MFI(e.g., ZSM-5), MWW (MCM-22 family), MEL (e.g., ZSM-11), MTW (e.g.,ZSM-12), or EUO (e.g., EU-1) structure type, or any member of theferrierite, faujasite, mordenite, or structure zeolite L or zeoliteBeta. It is one of the surprisingly discoveries of the present inventionthat in embodiments multidimensional zeolites can produce octenes with<10% triple branching and <1.9 branch index from highisobutene-containing feedstocks such as raffinate-1 by proper choice ofreaction conditions. The term uni-dimensional means that the poresystems do not interact, i.e., there is a single pore throughout thezeolite, in contast to multidimensional systems, wherein the poresystems intersect,

The one or more catalysts may be fully protonated, i.e. substantiallyall acid sites are in proton form or they may be partially protonated. Amixture of fully protonated and partially protonated catalysts may beused.

Without wishing to be bound by theory, the catalysts of the inventionproduce double and triple-branched octenes from isobutene containingfeedstocks as the kinetic products (products at low feedstock olefinconversions). The kinetic products are converted by secondaryisomerization reactions into the desirable lower-branched isomers. Byfinding reaction conditions at which secondary isomerization proceeds atsimilar rates to oligomerization, catalysts that produce triple-branchedisomers as the dominant product at lower conversion can surprisinglyproduce, in preferred embodiments, a product with <10 wt % triplebranched octene isomers at between 80 and 95% olefin conversion.

Octene product quality is a surprisingly strong function of temperatureand feedstock olefin conversion. By operating at high single passfeedstock conversion (preferably 80-95 wt %; unless otherwise specifiedthis means a weighted average of the individual conversions of all theolefin isomers in the feedstock) and a cycle-average reactiontemperature of between 220 and 320° C. (such as between 230 and 310° C.,in excess of 240 and 300° C. or in excess of 240 and 290° C.; alsocontemplated as preferred embodiments are any of the aforementionedlower ranges to any of the aforementioned upper ranges, such as 230 to300 or 290 C., in excess of 240 to 320 or 310° C., and so on), apractical means is provided to use “non-selective” multi-dimensional 10and 12 ring zeolite catalysts to produce higher olefin products suitablefor the production of plasticizer alcohols. At least some of theobjectives of the invention, such as in preferred embodiments triplebranching of <10 wt % and BI of <1.9, are achieved within the preferredolefin (butenes) conversion of 80-95%.

It will be appreciated by one of skill in the art in possession of thepresent disclosure that at the start of cycle where temperature islower, excellent product quality can none-the-less be achieved byoperating at a higher conversion. At high conversions, secondary olefindisproportionation and oligomerization reactions become more important.Selectivity to octenes using a raff-1 feedstock can declinedramatically. This provides an economic incentive to operate at lowerolefin conversion. While the directional response of product selectivityto conversion is not particularly surprising, the response totemperature is highly surprising. Increasing reaction temperature forraff-1 feedstock conversion improved catalyst activity, selectivity, andstability. The prior art, in contrast, emphasizes the need to find highactivity catalysts which can operate a low temperature where improvedselectivity is typically believed to occur. Thus, contrary to what wasknown, the most preferred solution according to the present invention isa less active multi-dimensional zeolite catalyst operating at arelatively high temperature for olefin oligomerization.

In preferred embodiments the catalyst contains a zeolite of the MFSstructure type, such as ZSM-57 as disclosed in, for instance,EP-B-174121, U.S. Pat. Nos. 4,873,067 and 4,973,781.

Zeolite catalysts having crystal structures that are essentially thesame as the MFS crystal structure but differing slightly therefrom inchemical composition may also be used, such as, zeolite catalystsobtained by removal of a number of aluminum atoms from, or by steamingof the zeolite, or zeolite catalyst obtained by addition of differentelements, for example, by impregnation or cation exchange or byincorporation during the zeolite synthesis.

ZSM-57 crystals may be prepared by any suitable method, for example, byheating a reaction mixture containing a source of silicon oxide and asource of aluminium oxide. The crystals are then generally calcined inair or oxygen at a temperature exceeding 500° C., for example, at atemperature of 510 or 550° C. for, for example, 10 to 20 hours. Thecalcined material is preferably exchanged with ammonium ions (NH₄ ⁺) andsubjected to conditions under which the ammonium ions decompose, withthe formation of ammonia and a proton, thus producing the acid form ofZSM-57. The zeolite may be fully protonated, i.e. substantially all acidsites are in proton form. Alternatively, the zeolite may be partiallyprotonated. The acid form may also be obtained by acid exchange with,for example, hydrochloric acid.

Catalysts suitable for the present invention are commercially availableand/or made by procedures known in the art. For instance, ZSM-57,ZSM-12, and MCM-22 family catalysts are commercially available fromExxonMobil Chemical Company. FAU, beta, ZSM-5, and mordenite arecommercially available from PQ, Engelhard, and SudChemie.

A modified ZSM-57 may also be used. The term “modified” means ZSM-57formed by a method in which an organic substance (organic promoter ortemplate) is used to promote formation of aluminosilicate crystals(zeolite precursor crystals) having the desired MFS structure type. Theuncalcined zeolite precursor crystals are exchanged with ammonium ionsor protons, and the crystals are then calcined under conditions suchthat a portion of the organic promoter or of a decomposition productderived therefrom remains within the pores of the crystal.

Reference is made to the following documents disclosing the preparationof ZSM-57 or modified ZSM-57-containing catalyst: U.S. Pat. Nos.4,873,067, 4,973,781, EP-B1-174,121, EP-A-625132 as well as Ernst andWeitkamp in “Zeolite ZSM-57: Synthesis, Characterization and ShapeSelective Properties”, in “Catalysis and Adsorption Zeolites”, Ed. G.Öhlmann et al., Elsevier Science Publishers, B. V. Amsterdam.

While it is preferred that the catalyst comprises solely ZSM-57, inembodiments the zeolite crystals may contain a minor proportion ofanother crystalline material, such as another zeolite structure type orquartz.

The zeolite may be used in the form of powders (including powdersconsisting wholly or in part of single crystals), or the zeolitecrystals may instead be incorporated in shaped agglomerates, forexample, tablets, extrudates or spheres, which may be obtained bycombining the zeolite with a binder material that is substantially inertunder the conditions employed in the oligomerization process.

The zeolite catalyst may be present in amount of from 1 to 99% byweight, based on the combined weight of the zeolite and binder material.As binder material, any suitable material may be used, for example,silica, metal oxides, or clays, such as montmorillonite, bentonite andkaolin clays, the clays optionally being calcined or modified chemicallyprior to use. Further examples of suitable matrix materials includesilica-alumina, silica-berylia, silica-magnesia, silica-thoria,silica-titania, silica-alumina-magnesia, silica-alumina-thoria,silica-alumina-zirconia and silica-magnesia-zirconia.

In preferred embodiments using zeolites of the MFS structure type, thezeolite crystals may also be bound with another zeolite as disclosed forexample in U.S. Pat. Nos. 5,993,642, 6,039,864, EP-B-568,566,EP-B-793,634 and EP-B-808,298, all incorporated herewith by way ofreference.

The alkene-containing feedstock comprising isobutene, is contacted withthe molecular sieve catalyst, preferably a zeolite of the MFS structuretype, or catalysts having crystal structures that are essentially thesame as the MFS crystal structure, or modified MFS structure, as definedabove, under oligomerization conditions effective to produce a productcomprising octenes.

It should be noted that in practice carbonaceous deposits accumulate inthe pores of zeolite catalysts when contacted with alkene-containingfeedstocks. The deposits reduce the activity of the catalyst. Tocompensate for lost activity, the process of the invention increases thereaction temperature with time on stream. The triple branchiness andbranch index of the products produced decrease with increasing reactiontemperature. The process of the invention preferably produces a productwith <10 wt % triple branched octenes and a total branch index of <1.9at the average reactor temperature across the full temperature range ofthe cycle. In preferred embodiments, the conditions include a start ofcycle temperature of from about 200° C., to about 250° C., such as about220° C., 230° C. or in excess of 240° C. (as measured by reactor inlettemperature), and an end of cycle temperature of from about 280 to 350°C., such as about 290° C. or 310° C. Preferred full cycle temperatureranges are from any temperature within the start of cycle temperaturerange, such as 220° C., to any temperature within the end of cycletemperature range, such as to 300° C. Thus, at least during part of thecycle, reactor inlet temperatures will be about 250, 260, 270, 280° C.,etc.

The pressure is preferably in the range of from 5 to 10 MPa, morepreferably, from 6 to 8 MPa and at an alkene weight hourly spacevelocity (WHSV) preferably in the range of from 0.1 to 40, morepreferably from 1 to 20, and most preferably from 3 to 12weight/weight·hour.

A desired conversion level is generally obtained by first selecting areaction temperature and by regularly adjusting this reactiontemperature to compensate for catalyst deactivation over time. Theprocess of the invention is highly selective at conversion rates as highas 95 wt %, typically comprised between 65 and 95 wt %, preferablycomprised between 80 and 95 wt %. These conversion rates may be achievedwithout recycle, i.e., they are single-pass conversion rates.

The process of the invention provides a product containing an oligomericproduct low in triple-branched octenes, and enriched in mono-branchedoctenes, which can be further transformed by any one or more of thefollowing steps: fractionation, hydrogenation, hydroformylation,oxidation, carbonylation, etherification, epoxidation, hydration, andthe like. Accordingly, the present invention also concerns higheraldehydes obtained by hydroformylation (such as by the Oxo Process),higher alcohols obtained by hydrogenation of the aforementioned higheraldehydes, and higher carboxylic acids obtained by oxidizing theaforementioned aldehydes or alcohols. (The term “higher” here simplymeans that the product has been oligomerized, e.g., dimerized, and thenincreased by one more carbon in the chain by the reaction with CO and H₂in the well-known Oxo or hydroformylation reaction). The process of theinvention also encompasses a process for the preparation of an ester ofa polycarboxylic acid in which the higher alcohols derived from theoligomeric product are reacted with a polycarboxylic acid underconditions suitable to make the polycarboxylic esters. Preferred estersare phthalic or adipic esters.

A particular advantage of the present invention is that raffinate-1 froma refinery or petrochemical process may be used as the feedstock withoutremoval of any or all of the isobutene present in the raffinate-1.

Raff-1 obtained from an FCC unit and or mixed FCC and coker andvisbreaking units is typically enriched in paraffins (isobutane andbutane). The higher paraffin content reduces the value of this type ofraff-1 stream vs. raff-1 obtained from steamcracking. Unlike raff-1 froma steamcracker, raff-1 can be produced without selective dienehydrogenation from an FCC unit. The process of the invention enablesproduction of plasticizers from FCC C4 olefins with minimal capitalcost. Raff-1 is distilled from the FCC unit, the contained C4 olefinsare converted to isononyl alcohols in high yield, and all the byproductscan be returned to the refinery for fuels blending.

Another particular advantage of the present invention is that theproduct of the oligomerization of raffinate-1 feedstock, as set forthabove, may directly and, in preferred embodiments, without furtherpurification, be contacted with a catalyst effective for the oxonationreaction, i.e., the transition metal catalyzed hydroformylationreaction, in the presence of CO and H₂ to provide a product comprisingpredominantly aldehydes containing one more carbon atom than the reactedolefin, and optionally then further reacted by hydrogenation, ifnecessary, to yield a C9 alcohol or reacted further by oxidation toyield a C9 carboxylic acid. In a particularly preferred embodiment, theC9 alcohols thus produced are converted to plasticizer by reaction withphthalic anyhydride, trimellitic anhydrides, adipic acid, and the like,to yield the corresponding tri- and/or di-substituted esters, which areparticularly useful plasticizers in PVC and other resins. The productsmay also be advantageously employed as detergent intermediates, e.g.,nonyl phenol.

The present invention has been described generally above, with referenceto certain embodiments. The following specific examples are provided as“representative” and, although they may describe preferred embodiments,are not intended to limit the invention.

Materials: (a) 50% ZSM-57/50% alumina catalyst purchased commerciallyfrom ExxonMobil Chemical Company, was provided in the form of extrudatein its activated hydrogen form, is crushed and sized to 0.3 to 1.0 mmparticles but otherwise used “as is”. Pure feedstockcomponents—n-butenes, isobutene and butanes are purchased from AirLiquide and used as received. Butene oligomerization is carried out witha 60 wt % butenes/40 wt % paraffin synthetic feedstock.

All experiments were conducted on standard pilot micro units withconditions chosen to closely emulate those used in commercialoperations, e.g.: 130-300° C. and 70 bar (7,000 kPa). The feedstock ispumped from 50 liter vessels using displacement pumps controlled by massflow meters. The feed is saturated with water by passing upwards througha vessel containing water at a constant 40° C. temperature. Afterexiting the hydrator the feed is pre-heated to the preselected heatertemperature and then runs downwards through a fixed-bed reactor equippedwith an internal thermowell. The oligomerization reaction is exothermicleading to a non-isothermal temperature profile down the length of thecatalyst bed.

No C2 or C1 gasses are fed or produced, and there is no evidence of anyfeedstock cracking. The product is cooled to near room temperature anddepressured to 20 bar. Total reactor effluent samples are taken at 20bar. After flowing through the sample vessels, the effluent isdepressured from 20 bar to atmospheric. Unreacted feedstock olefins andparaffins escape out the vent.

The total reactor effluent is analyzed by GC. The feed and productolefin/paraffin ratios are compared in order to measure conversion.Liquid product is analyzed on a standard commercial gas chromatograph(GC) equipped with a platinum catalyst to hydrogenate product olefins toparaffins. Carbon number distribution and paraffin distribution isdetermined. Conversion (%)=[1−{(A_(olefin)/A_(paraffins))/(A⁰_(olefin)/A⁰ _(paraffins))}]×100, where A=chromatographic peak area inproduct analysis (wt %) and A⁰=chromatographic peak area in feedanalysis (wt %). Selectivity is determined from gas chromatographic peakareas, after hydrogenation of the reaction product stream according tothe following equation: S_(Cn)=A_(Cn)/Σi A_(Ci), whereA_(Cn)=chromatographic peak area of all isomers with carbon number n,and A_(Ci)=chromatographic peak area of all isomers with carbon numberother than n. The terms “conversion” and “selectivity” are more fullydescribed in U.S. Patent Application No. 2004/0006250A1, andreference(s) cited therein The conversion and selectivity valuesreferred to hereinafter, including the claims, are for butene conversionand octene selectivity, unless otherwise stated.

EXAMPLE 1

Commercial ZSM-57/alumina extrudates were used to process 12 wt %isobutene/48 wt % n-butene/10 wt % isobutane/30 wt % n-butane feedstock.Reaction conditions were 70 bar, 15 WHSV, and 235° C. or 275° C.feedstock inlet temperature. Octenes selectivity vs. conversion isplotted using diamonds in FIG. 1. A single continuous curve is obtainedindicating that octenes selectivity is nearly independent of reactiontemperature. Product triple branching vs. butanes conversion is plottedusing diamonds in FIG. 2. The branch index data falls onto two separategroups. The group between 40 and 75% conversion forms a line at highertriple branching. The group between 70 and 95% conversion forms a lineat lower triple branching. Product branch index (BI) vs. conversion isplotted using diamonds in FIG. 3. The group between 40 and 75%conversion forms a line at higher branch index. The group between 70 and95% conversion forms a line at lower branch index. Triple branching andbranch index are proven to be a function of temperature. Highertemperature operation leads to a desirable reduction in octenes triplebranching and branch index.

EXAMPLE 2

Commercial ZSM-57/alumina extrudates were used to process 20 wt %isobutene/46 wt % n-butene/16 wt % isobutane/18 wt % n-butane feedstock.Reaction conditions were 70 bar, 15 WHSV, and 175° C. feedstock inlettemperature. Octenes selectivity vs. butanes conversion is plotted inFIG. 1. Percent triple branched isomers in the octenes (octene triplebranching) vs. conversion is plotted in FIG. 2. Octenes branching index(BI) vs. conversion is plotted in FIG. 3. At 175° C. the product retainshigh levels of triple branched products and high BI even at 95%conversion.

High temperature and conversion operation leads to a step-changedecrease in octenes triple branching. Above 90% conversion operating athigh temperature reduces the octenes triple branching content from 25 wt% in example 2 to below 5 wt % in Example 1 (FIG. 2). Between 75 and 85%conversion there is surprisingly no octenes selectivity penalty for thehigh temperature operation. Octenes triple branching decreases withincreasing conversion (FIG. 2).

The results show that even with isobutene/total butenes ratio greaterthan 0.10, an octene product is obtained with less than 10 wt % triplebranched product by operating at a sufficiently higher temperature. Thisis surprising, as well as contrary to the prior art, which teaches atriple branched content of greater than 10 wt % at an isobutene/totalbutenes ratio greater than 0.10. Without wishing to be bound by theory,the successful results suggest isomerization of double and triplebranched octenes to mono-branched octenes at much faster rates thanoligomerization to trimers and tetramers accompanied bydisproportionation. The preferred catalyst, ZSM-57, does a remarkablygood job of suppressing further oligomerization of octenes, whilefacilitating unimolecular isomerization. Prior to the present inventionit was believed that zeolites ZSM-22 and ZSM-23 were uniquely active forsecondary isomerization of octenes.

Trade names used herein are indicated by a ™ symbol or ® symbol,indicating that the names may be protected by certain trademark rights,e.g., they may be registered trademarks in various jurisdictions.

All patents and patent applications, test procedures (such as ASTMmethods, UL methods, and the like), and other documents cited herein arefully incorporated by reference to the extent such disclosure is notinconsistent with this invention and for all jurisdictions in which suchincorporation is permitted. When numerical lower limits and numericalupper limits are listed herein, ranges from any lower limit to any upperlimit are contemplated. While the illustrative embodiments of theinvention have been described with particularity, it will be understoodthat various other modifications will be apparent to and can be readilymade by those skilled in the art without departing from the spirit andscope of the invention. Accordingly, it is not intended that the scopeof the claims appended hereto be limited to the examples anddescriptions set forth herein but rather that the claims be construed asencompassing all the features of patentable novelty which reside in thepresent invention, including all features which would be treated asequivalents thereof by those skilled in the art to which the inventionpertains. Among those features, the preferred embodiment include: aprocess comprising contacting an isobutene-containing feed with amulti-dimensional molecular sieve catalyst containing at least one 10 or12 ring channel system under oligomerization conditions effective toproduce a product comprising octenes comprising less than about 10 wt %triple-branched octenes, based on the weight of said octenes, and havingan octenes branch index of <2, preferably wherein said conditions arecharacterized by a temperature, measured at the reactor inlet, fromabout 220° C. to about 320° C., or in excess of 240° C. to about 320°C.; or any of the aforementioned wherein said catalyst is selected fromZSM-57, ZSM-5, FAU, Beta, ZSM-12, mordenite, MCM-22 family, and mixturesthereof, particularly wherein said catalyst is selected from fullyand/or partially protonated ZSM-57, or wherein said catalyst comprisesat least 90 wt % fully and/or partially protonated ZSM-57; or any of theaforementioned wherein said feed comprises raffinate-1, which may befurther characterized as including greater than 10 wt % isobutene, basedon the weight of the olefins in said feed; or any of the aforementionedwherein said product comprising octenes comprising less than about 8 wt% triple-branched octenes, based on the weight of said octenes, orwherein said feed comprises from 12 to 40 wt % isobutene, based on theweight of the olefins in said feed, or wherein said feed comprises from12 to 34 wt % isobutene, based on the weight of the olefins in saidfeed, or wherein said feed comprises from 8 to 20 wt % isobutene, basedon the weight of the olefins in said feed; or any of the aforementionedwherein said product comprises less than 8 wt % triple-branched octene,or wherein said product comprises octenes having a branchiness of from1.7 to 2.2, or 1.6 to 2.1 or 1.5 to 2.0 or 1.4 to 1.9, or any of thelower BI given to any of the upper BI given; or any of theaforementioned wherein said conditions are further characterized aseffective for single pass butenes conversion of from 80% to about 95%,or wherein said conditions are further characterized as effective forsingle pass butenes conversion of about 80% to about 90%; or any of theaforementioned processes further comprising the step of contacting saidproduct comprising octenes with carbon monoxide and H₂ in the presenceof a hydroformylation catalyst under conditions effective to produce aC9 alcohol product, which may still be further be characterized asfurther comprising the step of contacting said C9 alcohol product withat least one acid or acid anhydride to produce an ester of said C9alcohol and said at least one acid or acid anhydride (such as whereinsaid at least one acid or acid anhydride is selected from phthalic acidand/or anhydride, mellitic acid and/or trimellitic anhydride, adipicacid, and mixtures thereof) and yet still further characterized ascomprising the step of mixing said ester with PVC to form a plasticizedPVC and extruding said plasticized PVC to form a shaped article.

The invention has been described above with reference to numerousembodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

1. A process comprising contacting an isobutene-containing feed having aisobutene/total butene ratio of greater than 0.10, with amulti-dimensional molecular sieve catalyst containing at least one 10 or12 ring channel system under oligomerization conditions effective toproduce a product comprising octenes, said conditions including atemperature, measured at the reactor inlet, in excess of 240° C. toabout 320° C., said octenes comprising less than 10 wt % triple-branchedoctenes, based on the weight of said octenes, and having an octenesbranch index of <2.
 2. The process of claim 1, wherein said catalyst isselected from ZSM-57, ZSM-5, FAU, Beta, ZSM-12, mordenite, MCM-22family, and mixtures thereof.
 3. The process of claim 2, wherein saidcatalyst is selected from fully and/or partially protonated ZSM-57. 4.The process of claim 1, wherein said catalyst comprises at least 90 wt %fully and/or partially protonated ZSM-57.
 5. The process of claim 1,wherein said feed comprises raffinate-1.
 6. The process of claim 1,wherein said product comprising octenes comprising less than about 8 wt% triple-branched octenes, based on the weight of said octenes.
 7. Theprocess of claim 1, wherein said feed comprises from 12 to 40 wt %isobutene, based on the weight of the olefins in said feed.
 8. Theprocess of claim 1, wherein said feed comprises from 12 to 30 wt %isobutene, based on the weight of the olefins in said feed.
 9. Theprocess of claim 1, wherein said feed comprises from 8 to 20 wt %isobutene, based on the weight of the olefins in said feed.
 10. Theprocess of claim 1, wherein said product comprises less than 8 wt %triple-branched octene.
 11. The process of claim 1, wherein said productcomprises octenes having octene branching index of less than 1.9. 12.The process of claim 1, wherein said conditions are furthercharacterized as effective for single pass butenes conversion of from80% to about 95%.
 13. The process of claim 1, wherein said conditionsare further characterized as effective for single pass butenesconversion of greater than 80% to about 95%.
 14. The process of claim 1,wherein said conditions are further characterized as effective forsingle pass butenes conversion of about 80% to about 90%.
 15. Theprocess of claim 1, further comprising the step of contacting saidproduct comprising octenes with carbon monoxide and H₂ in the presenceof a hydroformylation catalyst under conditions effect to produce a C9alcohol product.
 16. The process of claim 15, further comprising thestep of contacting said C9 alcohol product with at least one acid oracid anhydride to product an ester of said C9 alcohol and said at leastone acid or acid anhydride.
 17. The process of claim 16, wherein said atleast one acid or acid anhydride is selected form phthalic acid and/oranhydride, mellitic acid and/or trimellitic anhydride, adipic acid, andmixtures thereof.
 18. The process of claim 17, further comprising thestep of mixing said ester with PVC to form a plasticized PVC andextruding said plasticized PVC to form a shaped article.